Question

Which of the following statement is true about Nickel-Cadmium cell?

• A. Cell reaction is
  $Cd\left(s\right)+2Ni\left(OH{)}_3\right(s)\to Cd(s)+2Ni(OH{)}_2\left(s\right)+H_{2}O\left(l\right)$
• B. Cell reaction is
  $Ni+Cd{\left(OH\right)}_2\to Cd+Ni{\left(OH\right)}_2$
• C. $E_{cell}$ is constant because cell reaction has only pure solid/liquids
• D. $E_{cell}$ is constant due to presence of ions in cell reaction

Answer 1

The correct option is C $E_{cell}$ is constant because cell reaction has only pure solid/liquids

In Ni - Cd storage cell, the anode is consists of cadmium metal plate and cathode is consist of nickel dioxide. KOH is used as a electrolyte. Here, the positive plate ( cathode ) and negative plate (anode) are separated by a metallic sheet.
The overall cell reaction is,
$Cd\left(s\right)+2Ni\left(OH{)}_3\right(s)\to CdO(s)+2Ni(OH{)}_2\left(s\right)+H_{2}O\left(l\right)$

$E_{cell}=1.4V$
$E_{cell}$ is constant becuase the cell reaction has only pure solid/liquids.

Thus, (c) is true.